Fire and environmental officials were trying to determine Tuesday how a crude oil pipeline ruptured, spilling about 10,000 gallons of crude oil the area of the Oak Glen Nature Preserve in Hamilton County.

What neighbors thought was the smell of diesel, turned out to be documented by pictures from the EPA depicting oil sluggishly floating on a pond and a creek.

“It was quite strong this morning and helicopters start flying over continually around and around and around,” neighbor Ron Worsley said. “I guess if there are no fires or explosions.”

Hazardous materials crews and the Ohio Environmental Protection Agency were working with the pipeline company on cleanup efforts. An environmental cleanup company was called in to help, officials said. The Great Miami River was not affected, but EPA officials said a mile of creek was contaminated.

“We do have a large area impacted. The good news is it’s contained, the bad news is a mile of creek impacted,” Steve Renninger with the EPA said. “It is going to be a big cleanup.”

Renninger said oil leaked into a creek and collected in a marshy wetland, and it wasn't believed to have reached ponds or the Great Miami River. Rangers in the 294-acre nature preserve also were checking.

Cleanup crews had vacuum trucks at three work zone areas, including a football field-sized pond submerged with oil. The Health Department was also on scene conducting air quality checks.

“The Division of Wildlife has been out here to inspect, we’ve also walked it and we’ll continue to walk it looking for signs of impact,” Hamilton County Park Ranger Bob Mason said.

"It appears that there are natural barriers there that held in the oil that was released," Ohio EPA spokeswoman Heather Lauer said. She said a wetland of about 1 acre has been affected by oil.

The Mid-Valley Pipeline Co. pipeline is 20 inches wide and runs nearly 1,100 miles from Texas to Michigan. It is largely owned by Sunoco Logistics. In a news release, the company said it's estimated that 240 barrels of oil, about 10,000 gallons, leaked from the pipeline.

"We will coordinate with local, state and federal authorities on scene, with protection of the environment and property as our top priorities," the release stated.

Crews continued to work through the night. There will be another press briefing at 10 a.m. Wednesday where investigators hope to shed more light on how the pipeline broke and how extensive the environmental damage is.